The present invention relates to an image forming unit for supplying developer to a printer of an electro-photography type, a copier, and the like. The present invention also relates to an image forming apparatus having the image forming unit.
In a conventional image forming unit, a friction may be generated between a photosensitive drum and a developing roller during transportation thereof. Accordingly, when the conventional image forming unit forms an image for the first time after delivery, a density variance may occur due to insufficient charging.
In the conventional image forming unit, around the photosensitive drum having a surface with a static latent image to be formed thereon, there are provided a charging roller for uniformly charging the surface of the photosensitive drum, the developing roller for developing the static latent image with toner to form a toner image, and a cleaning roller for removing toner remaining on the surface of the photosensitive drum. The charging roller, the developing roller, and the cleaning roller are arranged to contact with the photosensitive drum.
In order to prevent the problem described above, when the conventional image forming unit is stored, a protective sheet is disposed between the photosensitive drum and the developing roller. The protective sheet has a three-layered structure formed of a urethane elastic sheet and a PET resin film attached to front and backside surfaces of the urethane elastic sheet. Accordingly, it is possible to prevent insufficient charging due to a stain on the surface of the photosensitive drum, thereby preventing a density variance such as a lateral streak after development (refer to Patent Reference).
Patent Reference: Japan Patent Publication No. 2003-156986
As described above, in the conventional image forming unit, the protective sheet includes the resin films formed of an insulation resin material and attached to the both sides of the elastic sheet. The photosensitive drum and the developing roller sandwich the protective sheet. Accordingly, when the protective sheet thus sandwiched is removed, frictional charging or separation charging occurs between the photosensitive drum and the developing roller. As a result, when the conventional image forming unit forms an image for the first time after delivery, a density variance such as a lateral streak may occur.
In view of the problems described above, an object of the present invention is to solve the problems of the conventional image forming unit, and to provide an image forming unit capable of reducing frictional charging and the like upon removing a protective sheet from the image forming unit, and reducing an image trouble when the image forming unit forms an image for the first time after delivery.
Further objects and advantages of the invention will be apparent from the following description of the invention.